High technology is progressing abruptly. Especially the technology for micro-electronic manufacture procedure is further innovated daily, so computer has already penetrated into each family and enterprise to become an indispensable electronic product in our daily lives. Following the prevalence of computer multimedia, more peripheral products are needed for the apparatus of input and output. And, because of the progress of the technology of the optical-electronic semiconductor, the product technology for relative peripheral devices for computer such as scanner, etc. has been more mature and prevalent, and nowadays it has become a necessary product in computer peripheral products.
Wherein, the scanner has further become an important peripheral device for computer for input and output. The scanner mainly applies a light-source module for providing light source incident upon an object to be scanned. And, an optical-length device is applied to receive the reflective image of the object to be scanned that is scanned by the light-source module. Again, a charge-coupled device is applied for picking up the image of the object to be scanned. After the image is converted into digital signals from the optical-electronic signals, they are finally transferred into a computer for proceeding image treatment.
Please refer to FIG. 1A and FIG. 1B, which are structure illustrations for the flatbed scanner used in prior arts. There is mainly a document window glass 12 arranged at the upper surface of the outer shell 11 of an optical scanner for placing an object to be scanned 80. A power source set 13 connected to a transmission mechanism 14 is arranged in the outer shell 11. The power source set 13 is made to output power through the transmission mechanism 14. The power is transferred to an optical chassis 15 that proceeds a linear motion along the direction of a guiding rod 16 in the hollow outer shell 11 for executing the image scanning job on the object to be scanned 80 that is placed upon the document window glass 12. The optical chassis 15 has a hollow shell body 151, a light source 152 located at an appropriate position of the upper side surface of the shell body 151, a plurality of reflective mirrors 153, a lens set 154 and a charge-coupled device (CCD) 155. The light emitted from the light source 152 is incident upon the object to be scanned 80. After the reflective light enters the shell body 151, and after it is reflected and direction-changed to increase its optical length to an appropriate length by a plurality of reflective mirrors 153, it becomes an image on the charge-coupled device 155 through the focusing of the lens set 154. The charge-coupled device 155 then converts the scanned image data into treatable electronic signals.
Please refer to FIG. 2A and FIG. 2B, which are illustrations for an automatic document feeder provided in a flatbed scanner of the prior arts. When the flatbed scanner proceeds document-feeding-typed scanning, and after the flatbed scanner 1 carries an automatic document feeder 2 and moves the optical chassis 15 to the scanning zone of the automatic document feeder 2, the optical chassis 15 is fixed. The automatic document feeder 2 is arranged a guiding groove 21. A scanning window 22 provided at an appropriate position of the guiding groove 21 may provide the optical chassis 15 to proceed image picking-up on the object to be scanned 80 that passes through the guiding groove 21. An image is generated by applying the light source 152 to the object to be scanned 80 through the processes of reflection or penetration. After the reflective light enters the shell body 151, and after it is reflected and direction-changed to increase its optical length to an appropriate length by a plurality of reflective mirrors 153, it becomes an image on the charge-coupled device 155 through the focusing of the lens set 154. The charge-coupled device 155 then converts the scanned image data into treatable electronic signals.
Please refer to FIG. 3A and FIG. 3B, which are the cross-sectional illustrations for the side view for the object to be scanned that is fed by the automatic document feeder of the prior arts. The guiding groove 21 arranged by the automatic document feeder 2 has an appropriate accommodation space for providing the pass for the object to be canned that has different thickness. When a feeding roller 23 feeds the thinner object to be scanned 80a to the scanning window 22, the thinner object to be scanned 80a is kept a depth of field height h with the scanning window 22. The depth of field height h is longer than the depth of field height h′ of the fed thicker object to be scanned 80b. Therefore, it causes an error of optical length for the optical chassis (not shown in the drawings) to pick up the image for the object to be scanned 80. So, sometimes the image of the object to be scanned 80 formed on the charge-coupled device (not shown in the drawings) is clear, and sometimes the scanned out image is vague. In order to use a more convenient way in automatic document-feeding-typed scanning, the consumers only have to accept the image clearness of the object to be scanned 80 in an appropriate degree. Therefore, for the businessmen engaged in the relative fields of scanner, they devote all their efforts to the research of perfect methods for solving this kind of problem to enhance the industrial competition abilities.